1. Field of the Invention
The present disclosure relates to an oil separator for returning oil in a refrigerant discharged from a compressor back to the compressor and a refrigeration cycle apparatus using the oil separator, in a refrigeration cycle of, for example, an ultracold freezer and the like.
2. Description of the Related Art
An ultracold freezer such as that used in, for example, research facilities and the like includes a refrigeration cycle configured to have a refrigerant circuit with a compressor, a condenser (radiator), a pressure reducer, an evaporator and the like sequentially and circularly connected. Although the refrigeration cycle has filled therein together with the refrigerant a predetermined amount of oil for lubricating the sliding portion of the compressor, some of the oil would be discharged from the compressor together with the refrigerant into the refrigeration cycle.
When oil is discharged into the refrigeration cycle, this becomes the cause of inhibiting the circulation of the refrigerant in the pressure reducer and the evaporator, and exhausts the oil in the compressor to cause burning and the like. Therefore, an oil separator is interposed between the compressor and the condenser.
The oil separator is configured of a tank with a predetermined capacity, and refrigerant (including oil) discharged from the compressor flows into this tank. Means such as a filter is used to separate in the tank the oil contained in the refrigerant and allows only the refrigerant to flow out from the tank toward the condenser. And the tank stores therein oil.
A float is provided in the tank and the float moves up and down according to changes in the oil level in the tank. When the amount of oil in the tank increases and the float rises to a predetermined location in accordance with the increase in the oil level, the valve device opens to return the oil in the tank back to the suction side. Thereby, the oil discharged into the refrigeration cycle is returned to the compressor to solve the aforementioned problem (for example, see Japanese Patent Application Laid-open Publication No. 9-72635 Specification).
By the way, the pressure of the refrigerant discharged from the compressor is of an extremely high value such as 3 MPa when the compressor is operating. In contrast, the pressure drops to about 0.5 MPa when the compressor stops. Thus the pressure in the oil separator would change frequently between the high and low pressures so that the float may be damaged due to such pressure changes. If oil should enter from the damaged portion into the float, the float would lose buoyancy and would be inhibited from detecting the up-down movement of the oil level leading to the oil returning function being lost.
The present disclosure has been made in view of such background and it is therefore an object of the present disclosure to provide an oil separator that can reduce the risk of the oil entering into the float and a refrigeration cycle apparatus using the oil separator.